System and method to operate hvac system during voltage variation event

ABSTRACT

A controller for a heating, ventilation, and/or air conditioning (HVAC) system is configured to detect an input voltage received as a power supply by the HVAC system, determine the input voltage exceeds a threshold value, and identify a voltage variation event based on determining that the input voltage exceeds the threshold value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.16/828,813, entitled “SYSTEM AND METHOD TO OPERATE HVAC SYSTEM DURINGVOLTAGE VARIATION EVENT,” filed Mar. 24, 2020, which is herebyincorporated by reference in its entirety for all purposes.

BACKGROUND

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present disclosure andare described below. This discussion is believed to be helpful inproviding the reader with background information to facilitate a betterunderstanding of the various aspects of the present disclosure.Accordingly, it should be noted that these statements are to be read inthis light, and not as admissions of prior art.

Heating, ventilation, and/or air conditioning (HVAC) systems areutilized in residential, commercial, and industrial environments tocontrol environmental properties, such as temperature and humidity, foroccupants of the respective environments. An HVAC system may control theenvironmental properties through control of a supply air flow deliveredto the environment. For example, the HVAC system may place the supplyair flow in a heat exchange relationship with a refrigerant of a vaporcompression circuit to condition the supply air flow. The HVAC systemmay receive power from a power source in order to operate. For example,the power source may be an electrical utility grid or a generator thatis separate from the HVAC system. The HVAC system may continuouslyreceive an input voltage from the power source to power HVAC systemcomponents that enable conditioning of the supply air flow. However, insome circumstances, the input voltage received from the power source maynot enable the HVAC system to operate in a desirable manner. Forexample, a received input voltage may deviate from an expected inputvoltage and may affect the operation of the HVAC system.

SUMMARY

A summary of certain embodiments disclosed herein is set forth below. Itshould be noted that these aspects are presented merely to provide thereader with a brief summary of these certain embodiments and that theseaspects are not intended to limit the scope of this disclosure. Indeed,this disclosure may encompass a variety of aspects that may not be setforth below.

In one embodiment, a controller for a heating, ventilation, and/or airconditioning (HVAC) system is configured to detect an input voltagereceived as a power supply by the HVAC system, determine the inputvoltage exceeds a threshold value, and identify a voltage variationevent based on determining that the input voltage exceeds the thresholdvalue.

In one embodiment, a non-transitory, computer-readable medium includescomputer-executable instructions that, when executed by processingcircuitry, are configured to cause the processing circuitry to detect aninput voltage received by a heating, ventilation, and/or airconditioning (HVAC) system, compare the input voltage to a range ofvoltage values, determine the input voltage is outside of the range ofvoltage values, and identify a voltage variation event based ondetermining that the input voltage is outside of the range of voltagevalues.

In one embodiment, a heating, ventilation, and/or air conditioning(HVAC) system includes a compressor and a controller communicativelycoupled to the compressor and having a tangible, non-transitory,computer-readable medium with computer-executable instructions. Theinstructions, when executed by a processing circuitry, are configured tocause the processing circuitry to determine an input voltage value of aninput voltage received as a power supply by the HVAC system, identify avoltage variation event based on determining that the input voltagevalue is outside of a range of voltage values, and operate the HVACsystem based on identifying the voltage variation event.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of this disclosure may be better understood upon readingthe following detailed description and upon reference to the drawings inwhich:

FIG. 1 is a perspective view of an embodiment of a heating, ventilation,and/or air conditioning (HVAC) system for environmental management thatmay employ one or more HVAC units, in accordance with an aspect of thepresent disclosure;

FIG. 2 is a perspective view of an embodiment of a packaged HVAC unitthat may be used in the HVAC system of FIG. 1 , in accordance with anaspect of the present disclosure;

FIG. 3 is a cutaway perspective view of an embodiment of a residential,split HVAC system, in accordance with an aspect of the presentdisclosure;

FIG. 4 is a schematic of an embodiment of a vapor compression systemthat can be used in any of the systems of FIGS. 1-3 , in accordance withan aspect of the present disclosure;

FIG. 5 is a schematic of an embodiment of an HVAC system configured toreceive power from a power source, in accordance with an aspect of thepresent disclosure;

FIG. 6 is a flowchart of an embodiment of a method or process foridentifying a voltage variation event, in accordance with an aspect ofthe present disclosure;

FIG. 7 is a flowchart of an embodiment of a method or process foridentifying a voltage variation event, in accordance with an aspect ofthe present disclosure;

FIG. 8 is a flowchart of an embodiment of a method or process foridentifying a voltage variation event, in accordance with an aspect ofthe present disclosure; and

FIG. 9 is a flowchart of an embodiment of a method or process foroperating an HVAC system based on identification of a voltage variationevent, in accordance with an aspect of the present disclosure.

DETAILED DESCRIPTION

One or more specific embodiments will be described below. In an effortto provide a concise description of these embodiments, not all featuresof an actual implementation are described in the specification. Itshould be noted that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be noted that such a development effortmight be complex and time consuming, but would nevertheless be a routineundertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Additionally, it should be noted that references to “one embodiment” or“an embodiment” of the present disclosure are not intended to beinterpreted as excluding the existence of additional embodiments thatalso incorporate the recited features.

The present disclosure is directed to a heating, ventilation, and/or airconditioning (HVAC) system. The HVAC system may be operated viaelectrical power, which may be received from a power source that isseparate from the HVAC system. For example, the power source may be anelectrical grid source, such as a utility grid, or an electrical powergenerator to which the HVAC system is electrically coupled. Theelectrical power, which may include an input voltage, received from thepower source may be used to power certain components of the HVAC system,such as a controller, in order to regulate operation of the HVAC system.The electrical power may also power other components of the HVAC system,such as a compressor and/or a fan. During typical operation, the HVACsystem may operate in a normal operating mode to condition an air flow.As used herein, the normal operating mode refers to operation of theHVAC system when the input voltage received from the power source as apower supply is substantially equal to an expected input voltage value,such as 20 volts (V), 24 V, 30 V, or any other suitable voltage value.For example, during the normal operating mode, the input voltage may besuitable to operate components of the HVAC system at any desiredoperating parameter value of a full or possible range of operatingparameter values.

However, in some circumstances, the input voltage provided by the powersource may be different than the expected input voltage. As an example,the input voltage may be substantially lower than the expected inputvoltage, such as during a brownout event in which an electrical gridprovides a reduced voltage to the HVAC system. As another example, theinput voltage may be substantially greater than the expected inputvoltage, such as during a change in operation of the electrical grid. Inany case, the change in input voltage may not be caused by operation ofcomponents of the HVAC system, but may still affect the operation of theHVAC system. For instance, the input voltage may cause the HVAC systemto operate inefficiently. As an example, the input voltage may beinsufficient to enable operation of a component of the HVAC system at atarget operating parameter value. In certain embodiments, the deviatedinput voltage may cause the operation of the HVAC system to be suspendedor shut down. As a result, the HVAC system may not condition the airflow when receiving deviated or unexpected input voltages.

Thus, it is presently recognized that enabling the HVAC system to usethe deviated input voltage to condition the air flow effectively mayimprove the operation of the HVAC system. Accordingly, embodiments ofthe present disclosure are directed to identifying a voltage variationevent in which the input voltage deviates or substantially deviates fromthe expected input voltage and to adjusting the operation of the HVACsystem in response to identifying the voltage variation event. Forexample, the input voltage received from the power source may bemonitored and compared to an expected input voltage value. Based on thecomparison, a voltage variation event may be identified. In response toidentifying the voltage variation event, the HVAC system may operate ina de-rated operating mode rather than in the normal operating mode. Inthe de-rated operating mode, a currently active operating mode may beadjusted to account for the deviated input voltage received during thevoltage variation event. As a result, the HVAC system may continue toprovide effective conditioning capabilities while receiving deviatedinput voltages.

Turning now to the drawings, FIG. 1 illustrates an embodiment of aheating, ventilation, and/or air conditioning (HVAC) system forenvironmental management that may employ one or more HVAC units. As usedherein, an HVAC system includes any number of components configured toenable regulation of parameters related to climate characteristics, suchas temperature, humidity, air flow, pressure, air quality, and so forth.For example, an “HVAC system” as used herein is defined asconventionally understood and as further described herein. Components orparts of an “HVAC system” may include, but are not limited to, all, someof, or individual parts such as a heat exchanger, a heater, an air flowcontrol device, such as a fan, a sensor configured to detect a climatecharacteristic or operating parameter, a filter, a control deviceconfigured to regulate operation of an HVAC system component, acomponent configured to enable regulation of climate characteristics, ora combination thereof. An “HVAC system” is a system configured toprovide such functions as heating, cooling, ventilation,dehumidification, pressurization, refrigeration, filtration, or anycombination thereof. The embodiments described herein may be utilized ina variety of applications to control climate characteristics, such asresidential, commercial, industrial, transportation, or otherapplications where climate control is desired.

In the illustrated embodiment, a building 10 is air conditioned by asystem that includes an HVAC unit 12. The building 10 may be acommercial structure or a residential structure. As shown, the HVAC unit12 is disposed on the roof of the building 10; however, the HVAC unit 12may be located in other equipment rooms or areas adjacent the building10. The HVAC unit 12 may be a single package unit containing otherequipment, such as a blower, integrated air handler, and/or auxiliaryheating unit. In other embodiments, the HVAC unit 12 may be part of asplit HVAC system, such as the system shown in FIG. 3 , which includesan outdoor HVAC unit 58 and an indoor HVAC unit 56.

The HVAC unit 12 is an air cooled device that implements a refrigerationcycle to provide conditioned air to the building 10. Specifically, theHVAC unit 12 may include one or more heat exchangers across which an airflow is passed to condition the air flow before the air flow is suppliedto the building. In the illustrated embodiment, the HVAC unit 12 is arooftop unit (RTU) that conditions a supply air stream, such asenvironmental air and/or a return air flow from the building 10. Afterthe HVAC unit 12 conditions the air, the air is supplied to the building10 via ductwork 14 extending throughout the building 10 from the HVACunit 12. For example, the ductwork 14 may extend to various individualfloors or other sections of the building 10. In certain embodiments, theHVAC unit 12 may be a heat pump that provides both heating and coolingto the building with one refrigeration circuit configured to operate indifferent modes. In other embodiments, the HVAC unit 12 may include oneor more refrigeration circuits for cooling an air stream and a furnacefor heating the air stream.

A control device 16, one type of which may be a thermostat, may be usedto designate the temperature of the conditioned air. The control device16 also may be used to control the flow of air through the ductwork 14.For example, the control device 16 may be used to regulate operation ofone or more components of the HVAC unit 12 or other components, such asdampers and fans, within the building 10 that may control flow of airthrough and/or from the ductwork 14. In some embodiments, other devicesmay be included in the system, such as pressure and/or temperaturetransducers or switches that sense the temperatures and pressures of thesupply air, return air, and so forth. Moreover, the control device 16may include computer systems that are integrated with or separate fromother building control or monitoring systems, and even systems that areremote from the building 10.

FIG. 2 is a perspective view of an embodiment of the HVAC unit 12. Inthe illustrated embodiment, the HVAC unit 12 is a single package unitthat may include one or more independent refrigeration circuits andcomponents that are tested, charged, wired, piped, and ready forinstallation. The HVAC unit 12 may provide a variety of heating and/orcooling functions, such as cooling only, heating only, cooling withelectric heat, cooling with dehumidification, cooling with gas heat, orcooling with a heat pump. As described above, the HVAC unit 12 maydirectly cool and/or heat an air stream provided to the building 10 tocondition a space in the building 10.

As shown in the illustrated embodiment of FIG. 2 , a cabinet 24 enclosesthe HVAC unit 12 and provides structural support and protection to theinternal components from environmental and other contaminants. In someembodiments, the cabinet 24 may be constructed of galvanized steel andinsulated with aluminum foil faced insulation. Rails 26 may be joined tothe bottom perimeter of the cabinet 24 and provide a foundation for theHVAC unit 12. In certain embodiments, the rails 26 may provide accessfor a forklift and/or overhead rigging to facilitate installation and/orremoval of the HVAC unit 12. In some embodiments, the rails 26 may fitonto “curbs” on the roof to enable the HVAC unit 12 to provide air tothe ductwork 14 from the bottom of the HVAC unit 12 while blockingelements such as rain from leaking into the building 10.

The HVAC unit 12 includes heat exchangers 28 and 30 in fluidcommunication with one or more refrigeration circuits. Tubes within theheat exchangers 28 and 30 may circulate refrigerant, such as R-410A,through the heat exchangers 28 and 30. The tubes may be of varioustypes, such as multichannel tubes, conventional copper or aluminumtubing, and so forth. Together, the heat exchangers 28 and 30 mayimplement a thermal cycle in which the refrigerant undergoes phasechanges and/or temperature changes as it flows through the heatexchangers 28 and 30 to produce heated and/or cooled air. For example,the heat exchanger 28 may function as a condenser where heat is releasedfrom the refrigerant to ambient air, and the heat exchanger 30 mayfunction as an evaporator where the refrigerant absorbs heat to cool anair stream. In other embodiments, the HVAC unit 12 may operate in a heatpump mode where the roles of the heat exchangers 28 and 30 may bereversed. That is, the heat exchanger 28 may function as an evaporatorand the heat exchanger 30 may function as a condenser. In furtherembodiments, the HVAC unit 12 may include a furnace for heating the airstream that is supplied to the building 10. While the illustratedembodiment of FIG. 2 shows the HVAC unit 12 having two of the heatexchangers 28 and 30, in other embodiments, the HVAC unit 12 may includeone heat exchanger or more than two heat exchangers.

The heat exchanger 30 is located within a compartment 31 that separatesthe heat exchanger 30 from the heat exchanger 28. Fans 32 draw air fromthe environment through the heat exchanger 28. Air may be heated and/orcooled as the air flows through the heat exchanger 28 before beingreleased back to the environment surrounding the HVAC unit 12. A blowerassembly 34, powered by a motor 36, draws air through the heat exchanger30 to heat or cool the air. The heated or cooled air may be directed tothe building 10 by the ductwork 14, which may be connected to the HVACunit 12. Before flowing through the heat exchanger 30, the conditionedair flows through one or more filters 38 that may remove particulatesand contaminants from the air. In certain embodiments, the filters 38may be disposed on the air intake side of the heat exchanger 30 toprevent contaminants from contacting the heat exchanger 30.

The HVAC unit 12 also may include other equipment for implementing thethermal cycle. Compressors 42 increase the pressure and temperature ofthe refrigerant before the refrigerant enters the heat exchanger 28. Thecompressors 42 may be any suitable type of compressors, such as scrollcompressors, rotary compressors, screw compressors, or reciprocatingcompressors. In some embodiments, the compressors 42 may include a pairof hermetic direct drive compressors arranged in a dual stageconfiguration 44. However, in other embodiments, any number of thecompressors 42 may be provided to achieve various stages of heatingand/or cooling. Additional equipment and devices may be included in theHVAC unit 12, such as a solid-core filter drier, a drain pan, adisconnect switch, an economizer, pressure switches, phase monitors, andhumidity sensors, among other things.

The HVAC unit 12 may receive power through a terminal block 46. Forexample, a high voltage power source may be connected to the terminalblock 46 to power the equipment. The operation of the HVAC unit 12 maybe governed or regulated by a control board 48. The control board 48 mayinclude control circuitry connected to a thermostat, sensors, andalarms. One or more of these components may be referred to hereinseparately or collectively as the control device 16. The controlcircuitry may be configured to control operation of the equipment,provide alarms, and monitor safety switches. Wiring 49 may connect thecontrol board 48 and the terminal block 46 to the equipment of the HVACunit 12.

FIG. 3 illustrates a residential heating and cooling system 50, also inaccordance with present techniques. The residential heating and coolingsystem 50 may provide heated and cooled air to a residential structure,as well as provide outside air for ventilation and provide improvedindoor air quality (IAQ) through devices such as ultraviolet lights andair filters. In the illustrated embodiment, the residential heating andcooling system 50 is a split HVAC system. In general, a residence 52conditioned by a split HVAC system may include refrigerant conduits 54that operatively couple the indoor unit 56 to the outdoor unit 58. Theindoor unit 56 may be positioned in a utility room, an attic, abasement, and so forth. The outdoor unit 58 is typically situatedadjacent to a side of residence 52 and is covered by a shroud to protectthe system components and to prevent leaves and other debris orcontaminants from entering the unit. The refrigerant conduits 54transfer refrigerant between the indoor unit 56 and the outdoor unit 58,typically transferring primarily liquid refrigerant in one direction andprimarily vaporized refrigerant in an opposite direction.

When the system shown in FIG. 3 is operating as an air conditioner, aheat exchanger in the outdoor unit 58 serves as a condenser forre-condensing vaporized refrigerant flowing from the indoor unit 56 tothe outdoor unit 58 via one of the refrigerant conduits 54. In theseapplications, a heat exchanger 62 of the indoor unit functions as anevaporator. Specifically, the heat exchanger 62 receives liquidrefrigerant, which may be expanded by an expansion device, andevaporates the refrigerant before returning it to the outdoor unit 58.

The outdoor unit 58 draws environmental air through the heat exchanger60 using a fan 64 and expels the air above the outdoor unit 58. Whenoperating as an air conditioner, the air is heated by the heat exchanger60 within the outdoor unit 58 and exits the unit at a temperature higherthan it entered. The indoor unit 56 includes a blower or fan 66 thatdirects air through or across the indoor heat exchanger 62, where theair is cooled when the system is operating in air conditioning mode.Thereafter, the air is passed through ductwork 68 that directs the airto the residence 52. The overall system operates to maintain a desiredtemperature as set by a system controller. When the temperature sensedinside the residence 52 is higher than the set point on the thermostat,or the set point plus a small amount, the residential heating andcooling system 50 may become operative to refrigerate additional air forcirculation through the residence 52. When the temperature reaches theset point, or the set point minus a small amount, the residentialheating and cooling system 50 may stop the refrigeration cycletemporarily.

The residential heating and cooling system 50 may also operate as a heatpump. When operating as a heat pump, the roles of heat exchangers 60 and62 are reversed. That is, the heat exchanger 60 of the outdoor unit 58will serve as an evaporator to evaporate refrigerant and thereby coolair entering the outdoor unit 58 as the air passes over the outdoor heatexchanger 60. The indoor heat exchanger 62 will receive a stream of airblown over it and will heat the air by condensing the refrigerant.

In some embodiments, the indoor unit 56 may include a furnace system 70.For example, the indoor unit 56 may include the furnace system 70 whenthe residential heating and cooling system 50 is not configured tooperate as a heat pump. The furnace system 70 may include a burnerassembly and heat exchanger, among other components, inside the indoorunit 56. Fuel is provided to the burner assembly of the furnace 70 whereit is mixed with air and combusted to form combustion products. Thecombustion products may pass through tubes or piping in a heatexchanger, separate from heat exchanger 62, such that air directed bythe blower 66 passes over the tubes or pipes and extracts heat from thecombustion products. The heated air may then be routed from the furnacesystem 70 to the ductwork 68 for heating the residence 52.

FIG. 4 is an embodiment of a vapor compression system 72 that can beused in any of the systems described above. The vapor compression system72 may circulate a refrigerant through a circuit starting with acompressor 74. The circuit may also include a condenser 76, an expansionvalve(s) or device(s) 78, and an evaporator 80. The vapor compressionsystem 72 may further include a control panel 82 that has an analog todigital (A/D) converter 84, a microprocessor 86, a non-volatile memory88, and/or an interface board 90. The control panel 82 and itscomponents may function to regulate operation of the vapor compressionsystem 72 based on feedback from an operator, from sensors of the vaporcompression system 72 that detect operating conditions, and so forth.

In some embodiments, the vapor compression system 72 may use one or moreof a variable speed drive (VSDs) 92, a motor 94, the compressor 74, thecondenser 76, the expansion valve or device 78, and/or the evaporator80. The motor 94 may drive the compressor 74 and may be powered by thevariable speed drive (VSD) 92. The VSD 92 receives alternating current(AC) power having a particular fixed line voltage and fixed linefrequency from an AC power source, and provides power having a variablevoltage and frequency to the motor 94. In other embodiments, the motor94 may be powered directly from an AC or direct current (DC) powersource. The motor 94 may include any type of electric motor that can bepowered by a VSD or directly from an AC or DC power source, such as aswitched reluctance motor, an induction motor, an electronicallycommutated permanent magnet motor, or another suitable motor.

The compressor 74 compresses a refrigerant vapor and delivers the vaporto the condenser 76 through a discharge passage. In some embodiments,the compressor 74 may be a centrifugal compressor. The refrigerant vapordelivered by the compressor 74 to the condenser 76 may transfer heat toa fluid passing across the condenser 76, such as ambient orenvironmental air 96. The refrigerant vapor may condense to arefrigerant liquid in the condenser 76 as a result of thermal heattransfer with the environmental air 96. The liquid refrigerant from thecondenser 76 may flow through the expansion device 78 to the evaporator80.

The liquid refrigerant delivered to the evaporator 80 may absorb heatfrom another air stream, such as a supply air stream 98 provided to thebuilding 10 or the residence 52. For example, the supply air stream 98may include ambient or environmental air, return air from a building, ora combination of the two. The liquid refrigerant in the evaporator 80may undergo a phase change from the liquid refrigerant to a refrigerantvapor. In this manner, the evaporator 80 may reduce the temperature ofthe supply air stream 98 via thermal heat transfer with the refrigerant.Thereafter, the vapor refrigerant exits the evaporator 80 and returns tothe compressor 74 by a suction line to complete the cycle.

In some embodiments, the vapor compression system 72 may further includea reheat coil in addition to the evaporator 80. For example, the reheatcoil may be positioned downstream of the evaporator relative to thesupply air stream 98 and may reheat the supply air stream 98 when thesupply air stream 98 is overcooled to remove humidity from the supplyair stream 98 before the supply air stream 98 is directed to thebuilding 10 or the residence 52.

Any of the features described herein may be incorporated with the HVACunit 12, the residential heating and cooling system 50, or other HVACsystems. Additionally, while the features disclosed herein are describedin the context of embodiments that directly heat and cool a supply airstream provided to a building or other load, embodiments of the presentdisclosure may be applicable to other HVAC systems as well. For example,the features described herein may be applied to mechanical coolingsystems, free cooling systems, chiller systems, or other heat pump orrefrigeration applications.

The present disclosure is directed to systems and methods configured toidentify a voltage variation event and to operate the HVAC system inresponse to identifying the voltage variation event. In someembodiments, input voltages received from a power source as power supplymay be compared with an expected input voltage or value to identify thevoltage variation event. The voltage variation event may indicate thatthe input voltages received by the HVAC system are deviated inputvoltages. For example, the voltage variation event may be identified inresponse to a determination that the input voltage is greater than anupper threshold voltage or value or is less than a lower thresholdvoltage or value. In addition, the HVAC system may transition from anormal operating mode to a de-rated operating mode based onidentification of the voltage variation event. In the de-rated operatingmode, operation of a component of the HVAC system may be adjusted. Byway of example, a compressor may operate in a limited range of operatingparameters or operating parameter values or based on a particularoperating parameter or value. In any case, the HVAC system may operatein a manner that utilizes the deviated input voltage to continue tooperate to condition the air flow.

With the preceding in mind, FIG. 5 is a schematic diagram of anembodiment of an HVAC system 150, which may be any suitable HVAC system,such as packaged unit (e.g., the HVAC unit 12), a split system (e.g.,the residential heating and cooling system 50), a heat pump configuredto operate in either a heating mode or a cooling mode, or any other typeof HVAC system. The HVAC system 150 may be electrically coupled to apower source 152, which may be an electrical power source that providesthe HVAC system 150 with electrical power in order to operate componentsof the HVAC system 150. For example, the HVAC system 150 may include acontroller 154 configured to receive electrical power from the powersource 152 to operate various components of the HVAC system 150 (e.g.,the compressor 74 of the vapor compression system 72). The controller154 may include a memory 156 and processing circuitry 158, such as amicroprocessor. The memory 156 may include volatile memory, such asrandom-access memory (RAM), and/or non-volatile memory, such asread-only memory (ROM), optical drives, hard disc drives, solid-statedrives, or any other non-transitory computer-readable medium thatincludes instructions to operate the HVAC system 150. The processingcircuitry 158 may be configured to execute instructions stored on thememory 156 to control operation of various components of the HVAC system150. For example, the processing circuitry 158 may include one or moreapplication specific integrated circuits (ASICs), one or more fieldprogrammable gate arrays (FPGAs), one or more general purposeprocessors, or any combination thereof, to operate the HVAC system 150.

As discussed above, the HVAC system 150 may operate in the normaloperating mode while the power source 152 provides an expected amount ofelectrical power, such as an expected input voltage. In certainembodiments, the HVAC system 150 may also include a display 160, whichmay be used to display a current operating mode (e.g., to a user,operator, or technician). Thus, while the HVAC system 150 operates inthe normal operating mode, the display 160 may present informationindicative of the normal operating mode. However, in some circumstances,the power source 152 may not provide an expected amount of electricalpower to enable the HVAC system 150 to operate in the normal operatingmode. For example, the power source 152 may provide an input voltagethat deviates or significantly deviates from the expected input voltage.However, in accordance with present techniques, the HVAC system 150 maystill utilize the input voltage to operate and provide some conditioningfunctionality. As an example, the HVAC system 150 may be configured tooperate in a de-rated operating mode, and the controller 154 may causethe display 160 to output information and/or a notification indicativeof the de-rated operating mode. In additional or alternativeembodiments, the information and/or notification may be presented in adifferent manner. For instance, the controller 154 may output anotification to a mobile device, present a different visual output(e.g., flash a light), present an audio output, output the informationand/or notification in any other suitable manner, or any combinationthereof. In any case, the notification and/or information may notify theuser that the HVAC system 150 is operating in the de-rated operatingmode.

With this in mind, FIGS. 5-9 each illustrate an embodiment of a methodor process for operating the HVAC system 150. In particular, each methoddepicted via FIGS. 5-9 may be performed based on the electrical power,such as a measured value of the electrical power, received by the HVACsystem 150 via the power source 152. In certain embodiments, a singlecontroller, such as the controller 154, may be configured to executesome or all illustrated steps of one of the methods. In additional oralternative embodiments, one controller may execute a portion of thesteps of one of the methods, and one or more additional controllers mayexecute another portion of the steps. Furthermore, it should be notedthat the steps of each method may be performed differently, such as fordifferent embodiments of the HVAC system 150. By way of example,additional steps may be performed with respect to the steps depicted inFIGS. 5-9 . Additionally or alternatively, certain steps described inFIGS. 5-9 may be removed, modified, and/or performed in a differentorder. Moreover, it should be noted that each of the methods presentedin FIGS. 5-9 may be performed at the same time as one another or atdifferent times, such as in a sequential manner. Indeed, the steps forone of the methods may be performed in any suitable manner relative to astep for another method.

FIG. 6 is a flowchart of an embodiment of a method or process 180 fordetermining an identification procedure used to detect a voltagevariation event. In particular, the specific manner in which the voltagevariation event is identified may be based on the input voltage valuereceived from the power source 152. At block 182, the HVAC system 150 isoperated in the normal operating mode. For example, the operation ofeach component of the HVAC system 150 may be set to a desirable ortarget operating parameter value to condition an air flow. While theHVAC system 150 is operated in the normal operating mode, an inputvoltage may be received by the HVAC system 150 from the power source 152to be used for operating the HVAC system 150 in the desired manner. Theinput voltage may be detected to determine a value of the input voltage,as indicated at block 184.

The input voltage may also be compared with a first range of voltagevalues to determine whether the input voltage is outside of the firstrange of voltage values, as shown at block 186. For instance, adetermination may be made as to whether the input voltage exceeds afirst upper threshold voltage value, which may be greater than theexpected input voltage by a difference value and/or whether the inputvoltage is less than a first lower threshold voltage value, which may beless than the expected input voltage by another difference value. Insome embodiments, the particular first range of voltage values may bedependent on the particular operating mode of the HVAC system 150utilized at a time that the input voltage value is detected. Forexample, for a cooling mode of the HVAC system 150, the first upperthreshold voltage value may be 8 percent, 10 percent, 12 percent, oranother suitable percentage value greater than the expected inputvoltage, and the first lower threshold voltage value may be 8 percent,10 percent, 12 percent, or another suitable percentage value less thanthe expected input voltage. Moreover, for a heating mode of the HVACsystem 150, the first upper threshold voltage value may be 10 percent,12 percent, 15 percent, 18 percent, or another suitable percentage valuegreater than the expected input voltage, and the first lower thresholdvoltage value may be 10 percent, 12 percent, percent, 18 percent, oranother suitable percentage value less than the expected input voltage.In certain embodiments, the first range of voltage values may be thesame regardless of the operating mode of the HVAC system 150. It shouldalso be noted that in certain embodiments, the first upper thresholdvoltage value and the first lower threshold voltage value may eachdiffer from the expected input voltage by the same difference value(e.g., the same percentage). In other words, the expected input voltageis approximately in the middle of the first range of voltage values. Inadditional or alternative embodiments, the first upper threshold voltagevalue may differ from the expected input voltage by a differentpercentage or amount than that of the first lower threshold voltagevalue such that the expected input voltage is offset from the middle ofthe first range of voltage values.

If a determination is made that the input voltage is not outside of thefirst range of voltage values, the HVAC system 150 may continue to beoperated in the normal operating mode, and input voltages from the powersource 152 may continue to be detected and compared to the first rangeof voltage values. However, if a determination is made that the inputvoltage is outside of the first range of voltage values, anotherdetermination may be made regarding whether the input voltage is outsideof a second range of voltage values, as indicated at block 188. Thesecond range of voltage values may include a second upper thresholdvoltage value and a second lower threshold voltage value, each of whichmay differ from the expected input voltage by a greater difference valuethan that of the first upper threshold voltage value and of the secondupper threshold voltage value, respectively. In other words, thedifference between the second upper/lower threshold voltage values andthe expected input voltage may be greater than the difference betweenthe first upper/lower threshold voltage values and the expected inputvoltage. As an example, the first upper threshold voltage value may be20 percent, 22 percent, 25 percent, or another suitable value greaterthan the expected input voltage, and the lower threshold voltage valuemay be 20 percent, 22 percent, 25 percent, or another suitable valueless than the expected input voltage.

If a determination is made that the input voltage is outside of thesecond range of voltage values, a first voltage variation eventdetermination procedure may be performed, as indicated at block 190.That is, if the input voltage is determined to be greater than thesecond upper threshold voltage value or less than the second lowerthreshold voltage value, the first voltage variation event determinationprocedure may be performed. However, if the input voltage is determinedto be outside of the first range of voltage values but not outside ofthe second range of voltage values, a second voltage variation eventdetermination procedure may be performed instead, as shown at block 192.

FIG. 7 is a flowchart of an embodiment of the method or process 190 forperforming the first voltage variation event determination procedure,such as after the steps described with reference to the method 180 ofFIG. 6 have been performed. For instance, after a determination is madethat a received input voltage is outside of the second range of voltagevalues, the method 190 may be executed. During performance of the method190, input voltages may be continuously received via the power source152 and detected accordingly. The input voltages may also becontinuously compared with the expected input voltage, the first rangeof voltage values, the second range of voltage values, or anycombination thereof, such as at a frequency of every second, every fiveseconds, every ten seconds, or at any other suitable frequency or timeinterval. At block 210, a first timer is started to monitor a first timeduration in which received input voltages are outside of the secondrange of voltage values. In some embodiments, the first time durationmay indicate a consecutive amount of time in which the received inputvoltages have been outside of the second range of voltage values. If adetermination is made that a received input voltage is within the secondrange of voltage values, the first timer may be reset. For example, themethod 190 may restart to re-initialize the first timer, or the method180 may be performed such that the HVAC system 150 is operated in thenormal operating mode (e.g., block 182 of FIG. 6 ) upon a determinationthat the received input voltage is within the second range of voltagevalues. In additional or alternative embodiments, the first timeduration may indicate a total amount of time (e.g., within a timeinterval) in which the received input voltages have been outside of thesecond range of voltage values. That is, if a determination is made thatthe received input voltage is within the second range of voltage values,the first timer may be paused at a halted time but may not be reset.Then, if a determination is made that a subsequently received inputvoltage is outside of the second range of voltage values, the first timeduration may continue to be monitored and accumulated from thepreviously indicated halted time by the first timer.

At block 212, based on the first timer, a determination may be made thatthe received input voltages have been outside of the second range ofvoltage values for a first threshold time period. For example, the firstthreshold time period may be 30 seconds, 45 seconds, 1 minute, 3minutes, or any other suitable time period. In response to adetermination that the received input voltages have been outside of thesecond range of voltage values for the first threshold time period, avoltage variation event may be identified, as indicated at block 214.Accordingly, the voltage variation event is identified via the firstvoltage variation event determination procedure when a determination ismade that received input voltages have been outside of the second rangefor a time period that is greater than the first threshold time period.

FIG. 8 is a flowchart of an embodiment of the method or process 192 forperforming the second voltage variation event determination procedure,such as after the steps described with reference to the method 180 ofFIG. 6 have been performed. For instance, after a determination is madethat a received input voltage is outside of the first range of voltagevalues but within the second range of voltage values, the method 192 maybe executed. During performance of the method 192, input voltages may becontinuously received via the power source 152. Such input voltages mayalso be continuously compared with the expected input voltage, the firstrange of voltage values, the second range of voltage values, or anycombination thereof. At block 242, a second timer and a third timer areeach started to monitor a second time duration and a third timeduration, respectively. Thus, the second time duration and the thirdtime duration may be separately tracked during the method 192.

At block 244, a determination is made regarding whether the second timerhas indicated the received input voltages have been outside of the firstrange of voltage values for a second threshold time period. The secondthreshold time period may be greater or substantially greater than thefirst threshold time period, such as 100 seconds, 2 minutes, 6 minutes,10 minutes, or any other suitable time period. If the second timerindicates that the received input voltages have been outside of thefirst range of voltage values for the second threshold time period, thevoltage variation event may be identified at block 214. For example, ifthe second timer indicates that the input voltages received from thepower source 152 have stabilized at a voltage value that is outside ofthe first range of voltage values, the power source 152 may not beoperating or providing electrical power as expected (e.g., during abrownout event). In some embodiments, the second threshold time periodmay be a consecutive time period in which the received input voltageshave been outside of the first range of voltage values. Thus, the secondtimer may be reset when a determination is made that the received inputvoltages are within the first range of voltage values. In additional oralternative embodiments, the second threshold time period may be a totalamount of time (e.g., within a certain time interval) in which thereceived input voltages have been outside of the first range of voltagevalues.

In further embodiments, the second timer may additionally oralternatively be reset and/or paused in response to a determination thatthe received input voltages are trending toward the expected inputvoltage at a particular rate, such as at 0.1 V every 30 seconds, 0.5 Vevery 30 seconds, 0.1 V every 1 minute, 0.2 V every 10 seconds, or atany suitable rate. Accordingly, the voltage variation event may not beidentified when a determination is made that the received input voltagesare trending toward the first range of voltage values to enable the HVACsystem 150 to operate in the normal operating mode. For example,maintenance may have been performed on the power source 152 to enablethe power source 152 to begin providing voltages near the expected inputvoltage. Accordingly, the second timer may be reset to avoid prematureidentification of the voltage variation event.

However, if a determination is made that the received input voltageshave not been outside of the first range of voltage values for thesecond threshold time period based on the second timer, a furtherdetermination may be made regarding whether the received input voltageshave been outside of the first range of voltage values for a thirdthreshold time period based on the third timer, as shown at block 246.As an example, the third threshold time period may be 30 seconds, 45seconds, 1 minute, or any other suitable threshold time period less orsubstantially less than the second threshold time period. If the thirdtimer indicates that the received input voltages have not been outsideof the first range of voltage values for the third threshold timeperiod, the third timer may be continuously monitored. However, if adetermination is made that the received input voltages are within thefirst range of voltage values at any point, the third timer may bereset.

If the third timer indicates that the received input voltages have beenoutside of the first range of voltage values for the third thresholdtime period, a fourth timer (e.g., a trend timer) may be started, asindicated at block 248. The fourth timer may be used for monitoring aduration of a trend of the received input voltages. For example, inorder to determine the trend of the received input voltages, a mostrecently received input voltage may be compared with one or morepreviously received input voltages, as shown at block 250. In someembodiments, the most recently received input voltage may be comparedwith the most previously received input voltage. In additional oralternative embodiments, the most recently received input voltage may becompared with an average voltage value of input voltages received in aprevious time window, such as of input voltages received in the previous20 seconds, in the previous 30 seconds, in the previous 1 minute, or inany suitable time interval. In any case, as subsequent input voltagesare continuously received, the subsequent input voltages may be comparedwith a different (e.g., updated) set of previously received inputvoltages.

At block 252, a determination is made regarding whether the mostrecently received input voltage is trending away from the first range ofvoltage values based on the comparison between the most recentlyreceived input voltage with the one or more previously received inputvoltages. If a determination is made that the most recently receivedinput voltage is not trending away from the first range of voltagevalues, the fourth timer may be reset and/or paused, and the secondtimer and the third timer may be continuously monitored. However, if adetermination is made that the most recently received input voltage istrending away from the first range of voltage values, a furtherdetermination may be made as to whether the fourth timer indicates themost recently received input voltages have been trending away from thefirst range of voltage values for a fourth threshold time period (e.g.,a trend time duration), as indicated at block 254. By way of example,the fourth threshold time period may be 20 seconds, 30 seconds, 40seconds, 50 seconds, 1 minute, or any suitable time period. If thefourth timer does not indicate that the most recently received inputvoltages have been trending away from the first range of voltage valuesfor the fourth threshold time period, thereby indicating that therecurrently is not a variation trend, no further action may be performed,and subsequent input voltages may be compared with previously receivedinput voltages.

However, if the fourth timer does indicate that the most recentlyreceived input voltages have been trending away from the first range ofvoltage values for the fourth threshold time period, thereby indicatingan occurrence of a variation trend, the voltage variation event may beidentified at block 214. Accordingly, the voltage variation event may beidentified in response to a determination that voltage trend of thereceived input voltages is the variation trend, which may indicate thatthe input voltages are fluctuating away from the expected input voltage.In this manner, the method 192 may anticipate that the power source 152is not operating or providing electrical power as expected before theinput voltages received from the power source 152 have stabilizedoutside of the first range of voltage values. In certain embodiments,the fourth threshold time period may be based on a rate in which themost recently received input voltages trend away from the first range ofvoltage values. As an example, if a determination is made that the inputvoltages trend away from the first range of voltage values at a high orfaster rate, the fourth threshold time period may be shorter such thatthe voltage variation event is identified more quickly. As anotherexample, if a determination is made that the input voltages trend awayfrom the first range of voltage values at a low or slower rate, thefourth threshold time period may be longer such that the voltagevariation event is identified more slowly. In this way, the fourththreshold time period may be dynamically adjusted based on a determinedrate at which the received input voltages trend away from the firstrange of voltage values.

It should be noted that each of the methods 180, 190, 192 may beperformed after operation of the HVAC system 150 has stabilized. In thismanner, the methods 180, 190, 192 may avoid identifying the voltagevariation event based on a fluctuating operation of the HVAC system 150(e.g., during a start-up or initialization of an operating mode of theHVAC system 150) instead of based on unexpected operation of the powersource 152. To this end, the methods 180, 190, 192 may be performed atsome time interval after a change in operation of the HVAC system 150has initialized. For example, the method 180, 190, 192 may be performed1 minute, 2 minutes, minutes, or any suitable time after initiating aheating mode, initiating a cooling mode, suspending or terminating adefrost mode, or changing any other suitable operating mode of the HVACsystem 150.

FIG. 9 is a flowchart of an embodiment of a method or process 280 foroperating the HVAC system 150 in response to identifying a voltagevariation event. At block 282, information associated with the voltagevariation event is stored. Such information may include a certainquantity of received input voltages prior to identification of thevoltage variation event, the time (e.g., date, time of day) of theidentification of the voltage variation event, an operational status ofcertain equipment (e.g., an operating mode, an operating parametervalue) of the HVAC system 150, any other suitable information, or anycombination thereof. The information may be retrieved at a later time,such as during maintenance of the HVAC system 150. For example,information regarding the voltage variation event may notify an operatoror technician of the HVAC system 150 that the de-rated operating mode ofthe HVAC system 150 was caused by unexpected or deviated input voltagesreceived from the power source 152, rather than by a deviated operationof a component of the HVAC system 150. Additionally or alternatively,the display 160 may present the information to indicate that the HVACsystem 150 is operating in the de-rated operating mode. In any case, theinformation may indicate that the de-rated operating mode of the HVACsystem was caused by the power source 152, rather than by a component ofthe HVAC system 150. Therefore, for example, the user may avoidperforming unnecessary maintenance on the HVAC system 150.

At block 284, a determination may be made regarding whether a quantityof instances of voltage variation events have been identified within atime interval. For example, a determination may be made regardingwhether the quantity of instances exceeds 2, 3, 5, or any other suitablethreshold number of voltage variation events identified within a 2 hourtime period, a 4 hour time period, a 5 hour time period, a 10 hour timeperiod, or any other suitable time period. At block 286, in response toa determination that the quantity of instances exceeds the thresholdnumber, the HVAC system 150 may be locked out or operated in a lockoutmode. In the lockout mode, operation of the HVAC system 150 may besuspended or terminated such that the HVAC system 150 does not conditionan air flow. In some embodiments, the lockout mode may be a soft lockoutmode, and the HVAC system 150 may automatically re-initialize aconditioning operation (e.g., the normal operating mode) after a timeinterval (e.g., 30 minutes, 1 hour, 2 hours) has passed. In additionalor alternative embodiments, the lockout mode may be a hard lockout mode,and operation of the HVAC system 150 may not re-initialize until after auser, such as an operator or technician, performs maintenance (e.g.,executes a test operation, enters a code) on the HVAC system 150.

At block 288, if a determination is made that the quantity of instancesdoes not exceed the threshold number, the HVAC system 150 may beoperated in a de-rated operation. In certain embodiments, the de-ratedoperation of the HVAC system 150 may be based on a component of the HVACsystem 150, such as based on a specification of the compressor 74 whenthe HVAC system 150 is in an active operation (e.g., to condition an airflow, to defrost a heat exchanger). In an example, if the compressor 74is a variable capacity compressor and the HVAC system 150 is in activeoperation, the compressor 74 may be operated at a de-rated nominalcapacity, which may be determined during development, manufacture, ortesting of the compressor 74 and/or of the HVAC system 150. In anotherexample, if the compressor 74 is a single stage compressor and the HVACsystem 150 is in active operation, the operation of the HVAC system 150may be suspended or shut down, and an anti-short cycle delay period,which may be determined during development, manufacture, or testing ofthe compressor 74 and/or of the HVAC system 150, may elapse beforeoperation of the HVAC system 150 restarts. In a further example, if thecompressor 74 is a multi-stage (e.g., 2-stage) compressor, thecompressor 74 may transition to a first stage, a reduced stage, oranother predetermined stage, or operation of the HVAC system 150 may bemay be suspended or shut down (e.g., if the compressor 74 is currentlyoperating in the first stage), and the anti-short cycle delay period mayelapse before operation of the HVAC system 150 restarts. Moreover, ifthe HVAC system 150 is not currently operating when the voltagevariation event is identified, operation of the compressor 74 maycontinue to be suspended regardless of the specification of thecompressor 74.

At block 290, the input voltages received from the power source 152 arecontinuously monitored and detected while the HVAC system 150 operatesin the de-rated operation in order to determine the value of the inputvoltages. At block 292, a determination is made regarding whether thereceived input voltages have been within the first range of voltagevalues for a fifth threshold time period, such as based on a fifthtimer. For instance, the fifth threshold time period may be 100 seconds,200 seconds, 300 seconds, 500 seconds, or any other suitable timeperiod. If a determination is made that the received input voltages havenot been within the first range of voltage values for the fifththreshold time period, the HVAC system 150 may continue to operate inthe de-rated operation, and the input voltages received from the powersource 152 may be continuously monitored.

However, if a determination is made that the received input voltageshave been within the first range of voltage values for the fifththreshold time period, the HVAC system 150 may be operated in the normaloperating mode, as indicated at block 294. That is, such a determinationmay indicate that the input voltages received from the power source 152may no longer be fluctuating to cause an identification of anothervoltage variation event. In other words, the input voltages may havestabilized within the first range of voltage values.

The present disclosure may provide one or more technical effects usefulin the operation of an HVAC system. For example, the HVAC system mayreceive input voltages from a power source in order to operate andcondition an air flow. When the input voltages are substantially equalto an expected input voltage, the HVAC system may operate in a normaloperating mode. However, when the input voltages differ or substantiallydiffer from the expected input voltage, thereby indicating a voltagevariation event, the HVAC system may operate in a de-rated operatingmode. In certain embodiments, the voltage variation event may beidentified based on a comparison between the input voltages receivedfrom the power source and an expected input voltage value or a range ofvoltage values. In the de-rated operating mode, a component, such as acompressor, of the HVAC system may operate in a particular operation.The particular operation may be based on a predetermined (e.g., reduced)operating parameter that enables the component to effectively utilizethe input voltage to condition the air flow. As a result, the HVACsystem may continue to condition the air flow during the voltagevariation event. The technical effects and technical problems in thespecification are examples and are not limiting. It should be noted thatthe embodiments described in the specification may have other technicaleffects and can solve other technical problems.

While only certain features and embodiments of the disclosure have beenillustrated and described, many modifications and changes may occur tothose skilled in the art, such as variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, including temperatures and pressures, mounting arrangements,use of materials, colors, orientations, and so forth without materiallydeparting from the novel teachings and advantages of the subject matterrecited in the claims. The order or sequence of any process or methodsteps may be varied or re-sequenced according to alternativeembodiments. It is, therefore, to be understood that the appended claimsare intended to cover all such modifications and changes as fall withinthe true spirit of the disclosure. Furthermore, in an effort to providea concise description of the exemplary embodiments, all features of anactual implementation may not have been described, such as thoseunrelated to the presently contemplated best mode of carrying out thedisclosure, or those unrelated to enabling the claimed disclosure. Itshould be noted that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation specific decisions may be made. Such a development effortmight be complex and time consuming, but would nevertheless be a routineundertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure, without undueexperimentation.

1. A controller for a heating, ventilation, and/or air conditioning(HVAC) system, wherein the controller is configured to: detect an inputvoltage received as a power supply by the HVAC system; determine theinput voltage exceeds a threshold value; and identify a voltagevariation event based on determining that the input voltage exceeds thethreshold value.
 2. The controller of claim 1, wherein the controller isconfigured to operate the HVAC system in a de-rated operating mode inresponse to identifying the voltage variation event.
 3. The controllerof claim 1, wherein the controller is configured to determine that theinput voltage exceeds the threshold value by confirming that the inputvoltage exceeds the threshold value for a threshold time period.
 4. Thecontroller of claim 3, wherein the threshold value is a first thresholdvalue, and the controller is configured to: determine that the inputvoltage exceeds a second threshold value, wherein the second thresholdvalue is less than the first threshold value; and determine a trend ofthe input voltage while the input voltage exceeds the second thresholdvalue.
 5. The controller of claim 4, wherein the controller isconfigured to identify the voltage variation event in response todetermining the trend is not toward the second threshold value for atrend time duration.
 6. The controller of claim 5, wherein thecontroller is configured to determine the trend of the input voltage bycomparing the input voltage with a previously received input voltage. 7.The controller of claim 1, wherein the threshold value is a firstthreshold value that is greater than a second threshold value, and thecontroller is configured to identify the voltage variation event basedon determining that the input voltage is less than the second thresholdvalue.
 8. The controller of claim 1, wherein the controller isconfigured to present a notification indicative of the voltage variationevent in response to identifying the voltage variation event.
 9. Thecontroller of claim 8, wherein the controller is configured to presentthe notification on a display of the HVAC system.
 10. A non-transitory,computer-readable medium comprising computer-executable instructionsthat, when executed by processing circuitry, are configured to cause theprocessing circuitry to: detect an input voltage received by a heating,ventilation, and/or air conditioning (HVAC) system; compare the inputvoltage to a range of voltage values; determine the input voltage isoutside of the range of voltage values; and identify a voltage variationevent based on determining that the input voltage is outside of therange of voltage values.
 11. The non-transitory, computer-readablemedium of claim 10, wherein the range of voltage values comprises anupper threshold voltage value and a lower threshold voltage value, andthe instructions, when executed by the processing circuitry, areconfigured to cause the processing circuitry to identify the voltagevariation event based on determining the input voltage is greater thanthe upper threshold voltage value or is less than the lower thresholdvoltage value.
 12. The non-transitory, computer-readable medium of claim11, wherein the upper threshold voltage value and the lower thresholdvoltage value each deviates from an expected input voltage value by adifference value.
 13. The non-transitory, computer-readable medium ofclaim 12, wherein the range of voltage values is a first range ofvoltage values, the upper threshold voltage value is a first upperthreshold voltage value, the lower threshold voltage value is a firstlower threshold voltage value, the difference value is a firstdifference value, and the instructions, when executed by the processingcircuitry, are configured to cause the processing circuitry to: comparethe input voltage to a second range of voltage values, wherein thesecond range of voltage values comprises a second upper thresholdvoltage value and a second lower threshold voltage value, and the secondupper threshold voltage value and the second lower threshold voltagevalue each deviates from the expected input voltage value by a seconddifference value that is greater than the first difference value;identify the voltage variation event based on determining that the inputvoltage is outside of the first range of voltage values and within thesecond range of voltage values for a first threshold time period; andidentify the voltage variation event based on determining that the inputvoltage is outside of the second range of voltage values for a secondthreshold time period, wherein the second threshold time period is lessthan the first threshold time period.
 14. The non-transitory,computer-readable medium of claim 10, wherein the instructions, whenexecuted by the processing circuitry, are configured to cause theprocessing circuitry to: determine a quantity of instances in which thevoltage variation event has been identified over a time interval; andoperate the HVAC system in a lockout mode in response to determining thequantity of instances exceeds a threshold quantity.
 15. Thenon-transitory, computer-readable medium of claim 14, wherein theinstructions, when executed by the processing circuitry, are configuredto cause the processing circuitry to operate the HVAC system in ade-rated operating mode in response to determining the quantity ofinstances does not exceed the threshold quantity.
 16. Thenon-transitory, computer-readable medium of claim 15, wherein theinstructions, when executed by the processing circuitry, are configuredto cause the processing circuitry to: monitor subsequent input voltagesreceived during operation in the de-rated operating mode; determinewhether the subsequent input voltages have been within the range ofvoltage values for a threshold time period; and transition the HVACsystem from the de-rated operating mode to a normal operating mode inresponse to determining that the subsequent input voltages have beenwithin the range of voltage values for the threshold time period.
 17. Aheating, ventilation, and/or air conditioning (HVAC) system, comprising:a compressor; a controller communicatively coupled to the compressor andcomprising a tangible, non-transitory, computer-readable medium withcomputer-executable instructions that, when executed by a processingcircuitry, are configured to cause the processing circuitry to:determine an input voltage value of an input voltage received as a powersupply by the HVAC system; identify a voltage variation event based ondetermining that the input voltage value is outside of a range ofvoltage values; and operate the HVAC system based on identifying thevoltage variation event.
 18. The HVAC system of claim 17, wherein theinstructions, when executed by the processing circuitry, are configuredto cause the processing circuitry to operate in a de-rated operatingmode in response to identifying the voltage variation event.
 19. TheHVAC system of claim 18, wherein the instructions, when executed by theprocessing circuitry, are configured to cause the processing circuitryto operate the compressor at a de-rated nominal capacity, to operate thecompressor at a predetermined stage, to suspend operation of the HVACsystem and restart the operation of the HVAC system after an anti-shortcycle delay period, or any combination thereof, upon initialization ofthe de-rated operating mode.
 20. The HVAC system of claim 17, whereinthe HVAC system is configured to electrically couple to a power source,and the HVAC system is configured to receive the input voltage from thepower source.